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Re: [Amps] Pi-L In-circuit Adjustment Question

To: <amps@contesting.com>, "Mike" <k4gmh@arrl.net>
Subject: Re: [Amps] Pi-L In-circuit Adjustment Question
From: "Phil Clements" <philk5pc@tyler.net>
Reply-to: Phil Clements <philk5pc@tyler.net>
Date: Sat, 19 Feb 2005 15:14:58 -0600
List-post: <mailto:amps@contesting.com>
>    * Tune capacitor (C1) adjusted to give a 50 Ohm impedance reading on
> the Autek.  Note: The physical spacing between C1's stator and rotor seem
> to be in the proper range for the frequency.  (C1 is a Jennings UCS 400
> which makes it easy to see the position of the moveable part, the so called
> rotor, in relation to the fixed part, the stator.)
> However, the SWR reading is out of range of the Autek.  Made the same
> measurement at the circuit's output using a MFJ259 and got the same results.

Mike,
Set the tune C and load C to the values from the charts or formulas. Do not 
touch them after they are set.
Assuming that the L coil has been checked for proper value and installation, it 
is usually good to go as built.
You then adjust L1, the tank coil until you reach minimum VSWR on the 259B. 
Then 
you can re-touch C1 and C2 to obtain 50 ohms and 1:1 vswr on the 259B. When you 
are done, measure the values of C1, C2, and L1 to see what you ended up with in 
relation to your initial calculations. The three values should be in the ball 
park. Of course, if you are using a roller coil for L1, this can be done very 
quickly.

(((73)))
Phil, K5PC


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